This disclosure relates generally to semiconductor manufacturing, and more particularly to a method to detect photoresist residue.
In semiconductor manufacturing a process called etching is used to remove material from or between layers in the semiconductor device to form paths, sometimes called vias. These vias can be filled with metal to connect different layers of the semiconductor device to each other. Problems arise when an etchant is blocked while forming a via, resulting in an uncompleted path when an attempt is made to fill the partially formed via with electrically conductive material.
A blocked etchant can occur due to problems associated with the etching process or problems associated with the lithography process. Etching process problems include particles being present or introduced into the etchant path, which can stop or delay the etchant so that the path is not completely formed. Lithography process problems include when photoresist is developed on a surface during the lithography process, removing photoresist to expose portions of the surface, and a photoresist residue is left on the exposed surface that can stop or delay the etchant so that the path or via is not completely formed.
It is difficult to detect when an etchant has been blocked, and as semiconductor technology progresses into the sub-micron level it becomes a problem to determine whether the cause of the blockage is rooted in the etching process or the lithography process. It is desirable to determine the cause of these blocked etches so that the problem can be corrected in order to improve manufacturing efficiencies such as wafer yield.
Accordingly, it would be desirable to provide an improved method for detecting photoresist residue absent the disadvantages found in the prior methods discussed above.